Plant for the manufacture of bronze colors



E. KRAMER PLANT FOR THE MANUFACTURE OF BRONZE COLORS March 29, 1938.

1 Filed Aug. 9, 1934 m N v m n u ow m a m a a. R bw now an mm Q 9 Q 2 2 w A W Patented Mar. 29, 1938 UNITED STATES PLANT FOR THE MANUFACTURE OF BRONZE COLORS Erwin Kramer, Berlin, Germany, assignor to the firm of Hartstofi-Metall A. G. Hametag, Berlin-Kopenick, Germany Application August 9, 1934, Serial No. 739,121 In Germany August 9, 1933 Claims.

My invention relates to the manufacture of metal powders, more particularly bronze powders, which are composed of extremely fine very small leaves or laminae, and which when used 5 together with a suitable lacquer, or the like, constitute a paint of excellent covering capacity.

The plant or machine embodying the present invention permits the starting material, i. e. small pieces of the metal, chips, coarse powder, foil 1 waste and the like, to be transformed into finished polished bronze powder in one continuous operation without any danger of explosion.

In the machine according to my invention the starting material is first stretched or hammered out so as to become laminated, whereupon the fine particles are conveyed by a current of air into a sifter in which the finished particles are separated from the unfinished ones. These latter particles are returned to the laminating device in order to be hammered a second time,

whereas the finished particlesare carried further into a device in which they are separated from the air; this device may be a so-called cyclone separator. The separted particles,'i. e.

the bronze powder, are then conveyed to a suitable polishing machine.

While the bronze particles are conveyed from the sifter to the polishing machine air is excluded so that oxidation, heating and ignition resulting in an explosion are completely prevented. Extraordinarily fine bronze powder is particularly inclined to self-ignition when brought into contact with air or oxygen. The hammered and laminated particles are conveyed while hot from the one manufacturing phase to the other which is important inasmuch as the fat employed in the hammering phase does not become cold and can effectively be used in the polishing machine.

The polishing operation consists in subjecting the fine particles to the action of brushes, and since there is, practically, no oxide at all upon the particles treated according to this invention, the final product, i. e. the finished bronze powder,

has a very bright lustre.

The amount of fat supplied prior to, or during, the hammering and laminating operation can be reduced to a minimum, because the oxidation risk and the ignition danger are greatly diminished, and it is, therefore, possible to produce a bronze powder very poor in fat and, therefore, particularly useful for printing purposes.

Because the bronze powder requires a certain degree of heat while it is being polished, and

heat is also required for the proper distribution of the fat, the cooling down of the bronze while it passes through the machine, should be prevented as much as possible and it is, therefore, important to convey the bronze particles directly from the sifter to the polishing machine, with 5 complete exclusion of air. Also time and labor are saved.

When bronze powders. for pyrotechnical purposes are produced, in which case not only the thinness of the laminations or foil particles, but 10 also their smallness must be considered, a portion of the work of comminuting the already, sufiiciently thin particles can be carried out in the polishing machine, which renders the operation more economical. That is made possible, be- 15 cause only very little fat is required to hammer or laminate the foils, and because no additional supply of fat in the polishing machine takes place, the particles are thoroughly torn.

To reduce or entirely prevent'oxidation is important not only in the manufacture of easily ignitable aluminium bronze, but also as regards bronzes from other metals, for instance the socalled gold-bronzes which are made from base metals. In these bronzes oxidations pause changes of the colors or tints, which changes generally are very undesirable sincethey impair the value of the bronzes. a

Another important feature of my improved plant resides in this, that the conveying air current circulates only through the hammering machine, the sifter and the cyclone separator, but not through the polishing machine, because otherwise the metal particles would be whirled up which would be detrimental to the action of the 35 brushes of this machine.

On the other hand,it is important that powders having a tendency to self-ignition receive a protective film of an oxide prior to leaving the polishing machine. This is a requisite especially 40 if the formation of an oxide film has been intentionally diminished during the hammering phase. Therefore, care must be taken that a suflicient amount of oxygen is supplied to the polishing drum for that purpose. However the flow of the 45 oxygen or oxygen containing gas through that drum is so controlled that the particles of the bronze are not whirled up. The gas flows through the drum in counter-direction to the direction of the bronze particles, and from the drum it is 50 led through the sifter etc., the gas leaving the plant finally at the place when the materialis fed to the hammering device, so that there is a? true counter-current between the gas and the metallic particles.

The gas mixtures leaves the 55 of Fig. 1, and Figure 3 is a transverse section in plane C-D of Fig. 1.

On the drawing, I (Figs. land 2) denotes a horizontally disposed rotary drumwhich is supported on rolls 3 and 4 by which it is rotated. Within said drum are axially arranged radially directed partition walls I by which. small steel balls 2 are carried upwardly as the drum is being rotated. The drum contains the metallic pieces,"

etc, to behammered and comminuted, (laminated) which "is effected by the steel balls as they continually fall down upon the metallic pieces carriedlikewise round by the partition walls I. The rolls 3 and 4 are rotated by any suitable means (notshownL The pipe- 5 for supplying the material to be treated and the pipe 6 for withdrawing thetreated material are, of course, stationary, but at their ends where they join the drum I, they are packed to prevent-any communication with the outer air. H I V The material to be treated is contained in an uprightfunnel-shaped receptacle 1 which is connectedat its lower end with the pipe 5 by means of a branch 3"o f this pipe and by means of a socalled sluice 8 in which a distributing member is rotated by any suitable means whereby the material is fed in uniform amounts through the pipe 5 into the drum. I

-I4 denotes;a fan which is likewise connected with the pipe5 by means of a branch I2 of the same and apipe I3. The current of air produced by the fan and flowing through the drum carries along with it the fine particles of the material to be treated, the mixture then passing on through the pipe 6 into the sifterIO which is connected at lts'lower end with the pipe 5 by means of a sluice II resembling the sluice 8' and being likewise continually rotatedl Those comminuted metal particles which are not yetsufliciently small are returned to the drum I through the sluice I I and the pipe 5, whereas the sufliciently'flne particles are conveyed from the sifter I0 through the pipe I6 which terminates in the separator IT, a so-called cyclone separator.

At its bottom, the separator I1 is also furnished with'a rotary sluice I3, by which the separated particlesare conveyed through a pipe 2| to the polishing drurn which is stationary and in which rotate axially disposed brushes 24 that contact with the inner wall of the drum. These brushes arecarriedby a shaft 23 having at one of its outer ends-a pulley 22 by means of which the brushes are rotated. The bronze particles pass through the polishing drum from the left-hand end (Fig. 1) to the right-hand end, and the finished bronze powder leaves the drum through the branch pipe- 25 dropping into a collecting receptacle 26.

i If oxygen or an oxygen-containing gas is used, it is introduced into the drum 20 through the pipe 28. It is suflicient to use nitrogen containing a few percent of oxygen. The gas or gas mixture flows through the polishing drum and then further into the separator cyclone IIeither through a certain pressure slightly above the atmospheric pressure, say an excess of pressure of a few centimeters'of water-column, in order to completely prevent-entrance of atmospheric air even if leakages should arise.

I Irrespective of Whether the fan I4 runs at a "higher or lower speed, the pressure regulator permits only the predetermined amount of gas to escape. In the practical operation of the plant the gas may be introduced into the polishing drum through the pipe 28 with a pressure of about 50 mm. of mercury, whereas the regulator 35 is adjusted for a pressure of about from 38 to mm. The drop of from 10 to 12 mm. between the inlet and the outlet is sufiicient to drive an appropriate amount of gas through the plant. In many cases the fan I4 need run only temporarily, for instance with a pressure of 100 mm. of water column. Also this manner of operation does not vary the amount of gas discharged through the outlet, valve 36, because the regulator 35 maintains an exit pressure of 40 mm. of mercury. On the other hand also the supply of the gasentering through the pipe 28 with a pressure of about mm. of mercury is not disturbed, because the conveying air does not circulate through the polishing drum 20 which drum communicates with -L* the suction'side of the fan through the separator With this manner of supplying the gas no gas need be supplied through the separate gas supply pipe 30 which terminates in the pipe I5. Where such a special pipe is provided, it may be closed if the other way mentioned is used.

j The required amount of fat may be supplied through a pipe 21 terminating in the pipe 5 where it is forked. It is, however, also possible to' apply the fat directly to the metal pieces in the feeding receptacle 1.

For supplying fat to the polishing drum 20 a a separate vessel 32 is connected with the pipe 2I by means of a branch 3I into which a regulating valve may be inserted. Preferably, however, a rotary sluice 33 is used instead of said valve, the sluice supplying the fat in a uniform-manner. It is also possible to connect the pipe 3I directly to the drum 20. v

I wish it to be understood that the drawing shows merely a preferred embodiment of the plant. Various changes in the details may be made without constituting a departure from the invention. The rotary sluice I9 at the foot of the separator Il may, for instance, be dispensed with, if a continuous and uniform supply of the bronze powder to the polishing drum is not thought indispensably requisite. It is at any rate advantageous to make use of a polishing machine through which the powder passes uninterruptedly, as in the case illustrated in the drawing.

The tube 34 is preferably provided with a filter in order to prevent metal particles from passing 1 therethrough. Tubes like 34 may be provided;

of course, also at other places of the plant, if that is desired.

Because of the gas supply being provided at the suction side of the fan a certain slight pressure above atmospheric pressure existsalso at the place of lowest pressure, and by the use of the inert gas atmosphere within the plant the possibility is afforded to work with a temperature between and 0. As inert gas a gas resulting from the combustion of illuminating gas or from oil or coal etc. may be used, if that gas contains from 2 to 4% of oxygen. Also nitrogen with a corresponding percentage of oxygen may be used.

I claim:

1. A plant for the manufacture of bronze pow ders comprising, in combination, a comminuting machine, a machine for polishing the comminuted metal particles, a conduit between said machines for conducting the metal particles directly from said comminuting machine to said polishing machine, and means including air tight connections between said conduit and said machines to prevent uncontrolled contact of atmospheric air with the metal particles while in said machines and said conduit, and means for supplying oxygen in regulated amount to said polishing machine.

2. The method of manufacturing bronze powders which comprises comminuting metal while substantially excluding atmospheric air therefrom, conducting the comminuted metal, while excluding atmospheric air from contact therewith, to a polishing means, and polishing the comminuted metal while subjecting the same to contact with oxygen in amount only sumcient to produce a thin oxide film on the metal particles,

3. A plant for the manufacture of bronze powders comprising in combination, a comminuting machine, a machine for polishing the comminuted metal particles, a conduit between said machines for conducting the metal particles from said comminuting machine to said polishing machine, a separator included in said conduit, means including air-tight connections between said conduit, said separator and said machines to prevent uncontrolled contact oi atmospheric air with the metal particles while in said machines, said separator and said conduit, and means for supplying oxygen in regulated amount to said polishing machine.

4. The combination as specified in claim 3, including a sitter operatively connected with the discharge end of said comminuting machine and interposed between said comminuting machine and said separator, and air-tight packings in the connections between said comminuting machine and said sifter.

5. The combination as specified in claim 3, including a sitter operatively connected with the discharge end of said comminuting machine and interposed between said comminuting machine and said separator, air-tight packings in the connections between said comminuting machines and said sifter, and a fan interposed between said separator and the inlet end of said comminuting machine ER N 

